Preparation and characterization of a novel tetrakis(4-hydroxyphenyl)porphyrin-graphene oxide nanocomposite and application in an optical sensor and determination of mercury ions

Article abstract of DOI:10.1039/c5ra17047h

In this work, for the first time we report a highly specific and sensitive mercury ion (Hg²⁺) optical sensor (optode). The optode was prepared by recently synthesized nanocomposites, based on 5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin (THPP)

Full text of DOI:10.1039/c5ra17047h

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Preparation and characterization of a novel tetrakis(4-
hydroxyphenyl)porphyrin - graphene oxide nanocomposite and
application in an optical sensor and determination of mercury ion
Received 00th January 20xx,
Accepted 00th January 20xx
a,*
b
a, b
b
DOI: 10.1039/x0xx00000x
Rouholah Zare-Dorabei , Rahmatollah Rahimi , Asgar Koohi , Solmaz Zargari
www.rsc.org/
2+
In this work, for the first time we report a highly specific and sensitive mercury ions (Hg ) optical sensor (optode). The
optode was prepared by recently synthesized nanocomposites, based 5,10,15,20-tetrakis (4-hydroxyphenyl) porphyrin
(THPP) and graphene oxide nanosheets. In this nanocomposite, porphyrin was stabilized on the graphene oxide
nanosheets. X-ray diffraction (XRD), UV-Vis spectroscopy, field-emission scanning electron microscopy (FE-SEM) and FT-IR
2
+
were employed to characterize the prepared nanocomposite. In the prepared optical chemical sensor, formation of Hg -
ionophore complex between the mercury ions and the membrane phase, changes the UV-Vis absorbance of the sensor. To
improve the sensor response, the various experimental parameters such as pH, concentration of the THPP and the
graphene oxide nanosheets in the prepared nanocomposite were optimized. This optode exhibited a linear range of
-
9
-5
-1
−9
−1
6
.0×10 to 6.0×10 mol. L Hg(II) with a detection limit of 3.2×10 mol. L and a response time of ∼210 s. It manifests
advantages of low detection limit, fast response time, wide dynamic range, as good reversibility, high reproducibility and
2
+
3+
2+
2+
2+
2+
2+
also remarkable selectivity regarding to the number of transition metals ions (i.e. Pb ,Cr , Zn , Cd , Cu , Fe , and Ni ).
This optode was applied for determining the Hg(II) ions in water samples.
different contexts such as environmental, clinical and
industrial analysis. The application of optical chemical sensors
is highly regarded especially for the determination of trace
Introduction
Due to indiscriminate disposal of wastewater, heavy metal
pollution is a worldwide environmental concern. Wastewaters
from many industries such as metallurgy, chemical
manufacturing, and battery manufacturing contain many kinds
of toxic heavy metal ions. Mercury is a highly toxic heavy metal
which leads to human health problems and environmental
amounts of heavy metal ions in environment and a variety of
1
1, 12
water and food samples
.
Optical sensors are a type of chemical sensors which act on the
basis of changes in the optical properties. Optical properties
are changed due to the interaction between the analyte and
the receptor. The main part of the optical sensors is a sensitive
membrane which contains the detector. For the design of
optical chemical sensor a sensitive layer such as dye indicator
1
contaminations . The toxicity of mercury is more than lead and
arsenic, which leads to neuropsychiatric disorders, infertility in
men and women as well as premature aging. Currently, due to
increasing of utilization of mercury compounds in industry,
(
i.e. porphyrin compounds) must be established onto a
2
, 3
2
-5
polymer matrix such as PVC, MIP, and cellulose acetate
.
Hg(II) detection has gained so much attentions
.
Porphyrins have been studied as probe molecules in different
Design of monitoring systems such as optical chemical sensors
for the determination of very low concentrations of mercury
ions in water samples can be a very useful and effective
approach in the control and removal of pollutants from the
1
3
chemical sensors . Porphyrins are sensitive to metal ions and
act as strong ligands. Electron pairs of nitrogen atoms in the
center of the porphyrin ring keep the metal ions and therefore
1
4-20
6
, 7
the complex of porphyrin is formed
.
environment
.
The characteristic peaks of porphyrin in the UV-Vis spectra is a
strong absorption peak (Soret band) in the range of 400-420
nm and four weak absorption peaks (Q bands) in the range of
In recent years, extensive research is allocated to optical
8-10
chemical sensors . Optical chemical sensors are used in
5
00 -700 nm. These peaks relate to the π → π* electron
transfer of porphyrin unsaturated ligand. In metalloporphyrin,
relative to porphyrin, the Soret band shifts to higher
wavelengths and its intensity is reduced. This behavior
represents the sensing properties of porphyrin. Therefore,
porphyrins are a good candidate to use as a detector in the
optical sensors.
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Choosing a proper substrate and detector stabilizer, is a very
important issue as another part of the membrane components
in the optical sensors. A proper substrate should have suitable
functional groups to bind and stabilize the detector on the
plastic or glass fulcrum. Therefore, the principle objective of
the present research is to use a proper substrate to stabilize
the porphyrin detector. Graphene oxide nanosheets with
carboxyl, hydroxyl and epoxy functional groups are able to
2
1-23
binding and stabilizing the detector on the Fulcrum
. In
addition, porphyrin with high coordination ability to metal ions
is a suitable detector to determine low concentration of these
metal ions.
Scheme 1 The schematic illustration of the THPP
In this work, a new optical chemical sensor based on porphyrin
and graphene oxide nanosheets was designed. The optical
sensor was prepared by recently synthesized nanocomposites
based on 5, 10, 15, 20-tetrakis (4-hydroxyphenyl) porphyrin
synthesis.
Subsequently, 80 ml de-ionized water was added gradually and
the temperature was raised to 98 °C. The mixture was further
treated with 10 ml 30% H O solution. The precipitate was
(THPP) and graphene oxide nanosheets. It is expected that
2
2
porphyrin as the strong ligand and with proper optical
properties efficiently determines mercury ions. To improve the
sensor response, the various experimental parameters such as
pH, concentration of the THPP and the graphene oxide
nanosheets in the prepared nanocomposite were optimized.
obtained by filtration and washed with de-ionized water until
the pH was 6 and dried at 65 °C under vacuum.
Synthesis of GO–COCl
Briefly, in a typical reaction, 0.5 g GO–COOH was suspended in
3
2
0 ml SOCl and 5 ml DMF. The reflux was continued for 24 h
at 70°C under nitrogen atmosphere. The resultant solution was
filtered and washed with anhydrous tetrahydrofuran (THF) and
dried under vacuum (Scheme 2).
Experimental
Materials
All reagents were of the best available analytical reagent grade
2
and supplied from Merck Co., except HgCl which was supplied
from Aldrich Co. Buffer solutions (0.10 M) were prepared from
phosphoric acid/sodium hydroxide solutions and the pH were
adjusted by addition of sodium hydroxide solution. A stock
-3
solution of 10 M mercury ion solution was prepared by
weighing 0.0811 g of HgCl and setting the volume to 250 mL.
2
Lower concentrations were prepared by several dilution of the
stock solution with phosphate buffer, pH 7.5.
Synthesis of graphene oxide-tetrakis (4-hydroxyphenyl) porphyrin
(
GO-THPP)
Synthesis of THPP
THPP (Scheme 1) was prepared using a modification of Adler
24
and Longo method . Briefly in a typical reaction, 1.146 g 4-
hydroxybenzaldehyde was added in 170 ml of propionic acid.
After about 15 minutes, 6.0 g of fresh distilled pyrrole was
slowly added to the above solution and reflux continued for
Synthesis of covalently attached porphyrin graphene oxide
nanosheets nanocomposite (GO-THPP)
Briefly, in a typical reaction, 3 ml of triethyl amine and 15 ml of
DMF were added to a mixture of 30 mg GO–COCl and 60 mg
THPP at 80 °C for 72 h under a nitrogen atmosphere. Then, the
solution was cooled to room temperature, and then poured
into 250 ml diethyl ether to precipitate the product. The
precipitate was collected by centrifuging at 8000 rpm for 30
min. The supernatant which contains unreacted THPP, was
discarded and the precipitate was washed thoroughly. After
adding another 100 ml of diethyl ether, the mixture was
sonicated for 5 min and then centrifuged at 8000 rpm for 30
min to collect the GO-THPP. Finally, the precipitate was
180 min. The dark purple product was filtered and washed
thoroughly with ethanol until the filtrate became clear.
Synthesis of graphene oxide nanosheets (GO)
Graphene oxide nanosheets was prepared using a modification
2
5, 26
of Hummers and Offeman’s method
reaction, 1 g NaNO , 1 g graphite and 46 ml H
together in an ice bath. KMnO (6 g) was slowly added to the
. Briefly in a typical
3
2
SO were stirred
4
4
mixture. The mixture was then transferred to a 35°C water
bath and stirred for about 1 h until a thick paste was formed.
2
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washed with CHCl
3
five times following the above procedure. shown in Fig. 1B.
The schematic illustration of covalently linked GO–porphyrin
nanocomposites is shown in Scheme 3.
Characterization of graphene oxide nanosheets (GO)
The oxygen-containing groups on the surfaces of graphene
oxide nanosheets are characterized by FT-IR analysis (Fig.2A).
Different functional groups are found in the FTIR spectrum,
-
1
-1
i.e., C-O group at 1070 cm
,
C=O group at 1730 cm and C=C at
-1
1
625 cm
,which indicates that large amounts of oxygen-
containing functional groups exist on graphene oxide
nanosheets.
Scheme 3 The schematic illustration of the prepared
Gr-THPP.
Structural and spectroscopic characterization of the prepared
compounds
Characterization of THPP
UV-Vis spectroscopy is one of the most efficient techniques to
detect porphyrin compounds. Porphyrins have two
characteristic bands named Soret (380-450 nm) and Q (450-
700 nm), which both are related to the π → π* electron
transfer. Therefore, this method was used to identify the
porphyrin production during the synthesis process. Fig. 1A
shows the strong peak at 423 nm and four absorption band at
519, 557,563 and 595 nm. Therefore, the emergence of these
bands is a valid evidence for the correct synthesis of THPP.
The FT-IR spectrum of this compound showed the C=N
-1
vibration at 1468 cm and the N–H stretching bond at 3050-
-
1
3
150 cm . In addition, the peak corresponding to aromatic
-1
-1
ether at 1660 cm and the OH peak at about 3300 cm are
Fig. 2 A) FT-IR spectrum and B) XRD pattern of a)Graphite
and b) GO, C) UV-Vis absorption of GO in DMF.
The XRD pattern of graphite and graphene oxide nanosheets
are shown in Fig. 2B. For XRD, the interlayer spacing of the
materials is proportional to the degree of oxidation. The
diffraction peak at 2θ= 26.60° which corresponds to the
normal graphite spacing (002) of graphite plane, disappears in
the graphene oxide nanosheets. Therefore, no impurity of
graphite precursor was remained in the obtained graphene
oxide nanosheets. In the XRD pattern of graphene oxide
nanosheets, the peak centered at 2θ=9.2° is assigned to (002)
inter-planar spacing of ca. 9.6 °A.
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-1
The optical absorption measurements were carried out by UV- In addition, the peak around 1707cm is assigned to the
Vis spectrometry. Fig. 2C shows the optical absorption bending vibration of the C=N of the porphyrin ring.
spectrum of graphene oxide nanosheets. Graphene oxide The partial reduction of graphene oxide to graphene in the
nanosheets shows an absorption peak at 320 nm originating GO-THPP nanocomposite formation was also verified through
from the π →π* plasmon of C=C which agrees with the XRD analysis. The XRD pattern of GO-THPP shown in Fig.
2
7
literature value
.
4B.The broadened peak in the range of 2θ= 17-25°in the GO-
The SEM image (Fig. 3) shows that few layered graphene
oxides have been formed. Although the SEM image does not
estimate the layer numbers of the graphene oxide nanosheets,
Fig. 3 SEM images of GO nanosheets
exactly.
Characterization of GO-THPP
The FT-IR spectra were recorded using KBr plates in the range
of 500–4000 cm using a Nicolet 6700 FT-IR spectrometer. Fig.
4A shows the typical FT-IR spectrum obtained from the
prepared graphite oxide material.In the reaction process for
Fig. 4 A) FT-IR spectrum and B) XRD pattern of GO-
preparation of GO-THPP, porphyrin molecules were attached
on the surface of graphene oxide sheet and some part of
graphene oxide nanosheets was reduced to graphene. As
shown in the GO-THPP spectrum, the broad peak around 3420
THPP, C) UV-Vis absorption of GO-THPP.
THPP pattern is related to the characteristic peak of graphene
and graphene oxide. Therefore, in the preparation of GO-THPP
some part of graphene oxide was reduced to the graphene.
-1
cm was weakened obviously. The disappearing of this peak
demonstrates that the most hydroxyl groups of graphene
oxide nanosheets removed from its surface and can be
evidence for reducing of some part of graphene oxide
nanosheets to graphene. Besides, the small peak around 1700
The optical absorption measurements is a powerful method to
29
determine the presence of porphyrin in nanocomposites
.
Fig. 4C shows UV-Vis spectrum of graphene oxide–porphyrin
nanocomposites in DMF. In this spectrum the presence of GO
peak around 250 nm and the characteristic peaks of porphyrin
-1
cm is assigned to C=O stretching of the residual COOH groups
2
8
.
After covalent functionalization of graphene oxide nanosheets
(Soret and four Q peaks) can be valid evidence for the
-1
with porphyrins, a new peak at around 1582cm was appeared
corresponding to the C=C vibrations of porphyrins. In
comparison to the FT-IR spectra of GO-COCl and THPP, in GO-
presence of porphyrin and GO in the GO-THPP nanocomposite.
The scanning electron micrographs (SEM) for the GO
porphyrin nanocomposite materials demonstrate that
–
a
-1
THPP the peak of the CO group appeared at 1168 cm which
confirmed that the porphyrin molecules are covalently bonded
to the graphene oxide nanosheets via carboxylic acid linkage.
homogeneous system with a micrometer order of magnitude
was obtained. Fig. 5 shows the selected micrographs for GO–
THPP nanocomposite and graphene oxide nanosheets. A clear
difference between micrographs of graphene oxide
4
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-
1
nanosheets and GO–THPP is observed. As shown in Fig. 5B, a optode was regenerated in 0.2 mol L EDTA solution for 210 s
three-dimensional network of randomly oriented sheet-like and was ready to use several times.
structures are exhibited after the composition of GO with
porphyrin.
Results and discussion
Membrane preparation
Principle of the operation
A mixture of 0.6 mg GO-THPP nanocomposites, was dispersed
Tetrakis (4-hydroxyphenyl) porphyrin (THPP) contains
a
nitrogen donor atom which could form internal bonds with
soft metal ions such as Hg(II). THPP (Scheme 1) has high
affinity to make a complex with Hg(II) ions. Hg(II) ions form a
complex with the ligand when the organic membrane contacts
with the aqueous solution; therefore, the following ion-
exchange reaction takes place:
2
+
+
H
2
(L)(m) + Hg (aq) ↔ (L)Hg(m) + 2H (aq)
(3)
In this equation, ‘L’ is the ligand. It can be seen that by the
addition of the mercury ions in the aqueous solution, the
chromoionophore in the organic membrane is more
deprotonated. Fig. 6 shows the absorption spectra of the
optode with different concentrations of Hg(II) in the range 1.0
−
14
−
3
−1
×
10 to 1.0 × 10 mol L .
Fig. 5 SEM images of A) GO nanosheets and B) GO-THPP.
in 1.0 mL of DMF. The membrane solution was homogenized
with a magnetic stirrer for 15 min. A plexiglas slides with 9 mm
×
40 mm dimensions were fitted into standard
spectrophotometer cells. The slides were cleaned with
ethanol, then water and finally dried in an oven at 70°C. The
membranes were cost by pipetting 10 μL of the membrane
solution onto a plexiglas slide and spread with a spin coater to
deposit a uniform thin film on the glass substrates.
Measurement procedure
The membrane was conditioned by inserting it into a cell,
including 3 mL of phosphate buffer (pH 7.5). After 5 min, the
membrane absorbance was measured at 426 nm. Then, the
cell was filled with the Hg(II) standard solution and after 210 s
its absorbance was measured in the same wavelength. The
membrane response is defined as the ratio of the
concentration of the unprotonated form of the
chromoionophore [C] to the total amount which is presented
in the membrane [Ctot]:
(
1)
This figure indicates that by the addition of Hg(II) to the
Then, the value was calculated by the absorbance solution, the absorption of the membrane at 426 nm
measurements at the λmax of the protonated form of the decreased. The response of the membrane is defined as the
chromoionophore as:
Where A
is the absorbance value of the membrane containing ligand [C] to the total amount which is presented in the
completely protonated chromoionophore (i.e., at α=0), A
ratio of the concentration of the unprotonated form of the
P
is membrane [Ctot], i.e. α = [C]/[Ctot]. The following equation
gives the relative fraction of the deprotonated form of the
D
chromoionophore
:
the absorbance value for the membrane containing the
completely deprotonated chromoionophore (i.e., at α=1), and
A is the absorbance which is measured at any time with
different concentration of mercury ion. Then, the calibration
curve was obtained by plotting of (1−α) vs. log [Hg(II)]. The
Where A
P D
and A are the absorbance of the ligand when
completely protonated and deprotonated, respectively.
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Effect of sample solution pH
Dynamic range
The pH influence on the response of the proposed optical
sensor was studied in the range of 3.5–9.5 by changing the Under the optimum conditions, calibration graphs for Hg(II)
was constructed by the response function (1−α) values were
obtained at 426nm in different Hg(II) concentrations. Fig. 9
Fig. 7 The pH effect on the optode film response.
2
Fig. 9 Calibration curve for determination of Hg in
+
universal buffer. As it can be noticed in Fig. 7, as the pH of the
solution is increased the response of the membrane to Hg(II)
the optimum conditions
,
shows the calibration graph revealed that the signal is linear in
ions is increased. The sensor response is almost constant in the
pH range of 7-8. A maximum value in the optical sensor
-5
-9
the range of 6.0 × 10 to 6.0 × 10 with a regression equation
2
of (1−α) = −0.1211 (log [Hg(II)])−0.2106 , (R = 0.9976). The
response was obtained at pH value of 7.5
selected for the subsequent investigations.
. This pH was
detection limit (3S
b
/m) of the method was calculated as 3.2 ×
-9
1
0 , which indicates the proposed sensor is more efficient and
sensitive for mercury ion.
The observed drift at higher pH values could be attributed to
the hydrolysis of mercury ions in the solution which decrease
the Hg(II) ion concentration in the solution and inhibits the
Optode regeneration (Reversibility)
formation of a complex between Hg(II) ions and the THPP. For suitable performance of the optode membrane, its
Thus, the optode response decreases. At pH < 6, the absorbance change must be reversible. Primary tests were
heteroatoms of the ligand in the membrane of the optode are conducted with a number of reagents to reverse the
protonated and could not form complex with Hg(II) ions in the absorbance of Hg(II) complex. Complexing agents such as EDTA
solution.
and sulfosalcylic acid have a partial reverse effect, and
prolonged exposure to them have no further improvement in
reversibility of the optode. EDTA (0.2 M) was concluded to be
the best reagent, giving a short regeneration time (less than 3
min). To evaluate the discrepancies in the response for
successive runs using a single optode membrane, the
reproducibility was evaluated by performing 5 determinations
Response time
In this research, the optode film was found to reach 95-99% of
the final signal at 180-210 s, depending on mercury ion
concentration. Fig.8 shows the time course for the absorption
intensity of the membrane at 426 nm. The response time was
tested by recording the absorbance change from a pure buffer
-5
with the same Hg(II) standard solution. For 1.0 ×10 M Hg(II) a
drift of about 4.07% was obtained in the response of the
optode. Fig. 10 shows the absorbance changes versus time for
the optode membrane.
-5
(pH = 7.5) to a buffered Hg(II) solution of 1.0 × 10 M.
The response time of the optical sensor depended on the
organic membrane thickness, the organic membrane
composition, the concentration of the measuring ion and the
pH of the measurement. The response time of the optode in a
higher concentration of Hg(II) was restricted by the time
requested for the analyte diffusion from the bulk of the
solution toward the membrane. For highly diluted solutions,
the limiting step is the convective mass transport from the
bulk of the aqueous solution to the membrane.
Lifetime and stability
Fig. 10 An absorbance variation of the membrane
-
5
at 426 nm for repeatedly exposing into 1.0 ×10
M Hg(II) solution and 0.2 M EDTA solution.
6
| RSC
F
A
ig
d
.
v
8
.,
R
2
e
0
s
1
p
5
o
,
n
0
s
0
e
,
t
1i m- 3e curve of the optode at 426 nm
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The lifetime of the optode was determined by adding a buffer The recovery tests were performed using these three different
solution (pH=7.5) into the cuvette, containing the membrane. concentrations. The test for each sample was carried out in
The signal was recorded at a wavelength of 426 nm over a triplicate measurements and the results are given in Table 2.
period of time (about 10 h). No significant indicator loss As it is evident from Table 2, Hg(II) recovery values were
occurred during that time. When the film was exposed to light, between 98 and 104.
no drift in the signal took place and the optode was found to
be stable during the experiment with no indicator leakage.
Table 2 Results of the repeatability and recovery test.
Stability of film response was investigated over six weeks
under ambient conditions, which is indicated that the
Standard
Average
Hg(II) found
with optode
(M)
membrane was stable over this period.
Average
absorptio
n
concentrati
RSD (%) Recovery
ons
of
Effect of the foreign ions
(n=5
)
(%)
mercury
(n=5)
The interference for a number of common species of the
absorbance determination of Hg(II) ions was investigated using
the prepared sensor. To determine the selectivity of the
optode membrane, the optode membrane was tested under
(M)
(n=5)
-6
-6
6.0 × 10
0.7
6.28 × 10
4.33
104
-3
mercury ions concentration of 3×10 M in the presence of
other metal ions. Limit of tolerance was taken as the
concentration causing an error of ±5 % in the mercury ions
assay. The results are summarized in Table 1. The surprisingly
high selectivity of the optode membrane for Hg(II) ions over
other cations used, most probably arises from the strong
tendency of the THPP for formation of stable complexes with
Hg(II) ions.
-7
-8
-7
6
.0 × 10
0.7384
0.7758
5.96 × 10
3.34
5.09
99
-8
6
6
.0 × 10
6.017 × 10
101
-
8
.00 × 10
(Tehran
-8
0.769
5.89 × 10
4.91
98
River
water)
Table 1 Influence of the foreign ions on the Hg(II).
Conclusions
In this work, for the first time a highly specific and sensitive
optical sensor (optode) was developed based on the tetrakis
Species Relative error
2
%
Species
+
Na
Relative error
1.06
%
+
Cd
4.6
(
4-hydroxyphenyl) porphyrin (THPP) stabilized with graphene
oxide nanosheets for the determination of ultra-trace amounts
of Hg(II) ions. The sensor was easily prepared, readily
regenerated with a EDTA solution and demonstrated a long
lifetime. The optode response was concluded to be
reproducible with a good Hg(II) selectivity over other
potentially interfering ions. Since the optical sensor required
no solvent extraction, it could compete satisfactory with the
standard optical fibers. The characteristics of the proposed
Hg(II) ions optical chemical sensor were compared with other
2
+
2+
Pb
3.7
Fe
2.11
2.12
0.5
0.8
3.2
2.9
3.4
3.9
2
+
3+
Ni
3.1
Cr
2
+
+
+
Co
Cu
0.34
1.06
1.76
1.009
2.3
Ti
2
+
Cs
2
+
+
Zn
Ag
3
0-32
determination methods of literature in Table 3
. This
+
K
2+
optode was applied to the determination of Hg(II) in different
concentrations in water samples with good precision and
accuracy.
Mn
2
+
2+
Ca
Mg
+
3+
NH
4
1.1
Al
Repeatability and recovery tests
a
DL (M)
b
LR (M)
Method
SPE-AAS
R.S.D.% Samples Ref.
The repeatability was examined by preparing 15 different
membranes from the same mixture and measuring the
−
13
−13
6.0×10
3.0×10
-
13
4.7
water
water
water
30
31
32
−
-
6
4.0×10
−9
0 - 333.0×10 -
absorbance of each membrane at 426 nm in 6.0 × 10 , 6.0 ×
−
9
-
7
-8
0 and 6.0 × 10 mol.L Hg(II) (five replicate determinations)
-1
Colorimetric 4.0 ×10
Sensor
1
-
6
in the buffer solutions at pH 7.5. The RSD% for 6.0 × 10 , 6.0 ×
−
8
−6
-7
-8
and 6.0 × 10 mol.L were 4.33%, 3.34% and 5.09%,
-1
Colorimetric 4.0×10
Sensors
2.5 ×10
−
3.5×10
-
3.24-
4.53
10
5
respectively (Table 2). This result shows that the sensor has a
good repeatability.
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PAPER
RSC Advances
−
9
-5
Optiical
Sensor
3.2×10
6.0×10
6.0×10
-
4.41
water
This
27 M. A. Khaderbad, V. Tjoa, T. Z. Oo, J. Wei, M. Sheri, R.
Mangalampalli, V. R. Rao, S. G. Mhaisalkar and N. Mathews,
-
9
work
RSC Adv., 2012,
H. Zhang, X. Lv, Y. Li, Y. Wang, J. Li, ACS Nano, 2010,
86.
2, 4120–4124.
2
8
4, 380–
3
Acknowledgements
29 R. Rahimi, M. Mahjoub Moghaddas and S. Zargari, Sol-Gel
Sci. Technol., 2013, 65, 420-429.
The financial support of this study by Iran University of Science
and Technology and Nano Technology Initiative Concil are
3
0
E. Ziaei, A. Mehdinia and A. Jabbari, Anal. Chim. Acta, 2014,
50, 49-56.
8
gratefully acknowledged. The author acknowledges financial 31 J. Duan, H. Yin
,
014, 57, 139-142.
R. Wei and W. Wang, Biosens. Bioelectron.,
2
P. Jarujamrus, M. Amatatongchai, A. Thima, T.
support from the Iran National Science Foundation (INSF).
3
2
Khongrangdee and C. Mongkontong, Spectrochim. Acta A,
2
015, 142, 86-93.
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Optical chemical sensor for determination of mercury ion
1
27x97mm (96 x 96 DPI)